1. Field of the Invention
The present invention generally relates to an Integrated Circuit Card in which a semiconductor chip is embedded. Such Integrated Circuit Card is commonly referred to as IC card. More particularly, the present invention relates to a dual mode type IC card that has a contact-free mode and a contact mode. The contact-free mode is a mode where electrical energy is supplied from a reader/writer by an inductive coupling and a data transmission between the IC card and the reader/writer is performed by the inductive coupling. The contact mode is a mode where electrical energy is supplied from the reader/writer via a contact terminal of the IC card and the data transmission is performed via the contact terminal.
This application relies for priority on Japanese patent application, Serial Number 208556/2000, filed Jul. 10, 2000, which is incorporated herein by reference in its entirety.
2. Description of the Related Art
In such this technical field, an IC card of the dual mode type is described in, for example, U.S. Pat. No. 5,206,495 as a related art.
FIG. 2 is a schematic block diagram showing the IC card of the related art.
The IC card has a contact terminal 203, a coil 204 and a coil 205. The contact terminal 203 is contacted with a terminal of a reader/writer in the contact mode and receives electrical energy via the contacted terminal of the reader/writer. Bi-directional data transmission between the IC card and the reader/writer is executed via the contact terminal 203 in the contact mode.
The coils 204 and 205 are inductive coupled to a coil of the reader/writer in the contact-free mode and receive electrical energy. The coils 204 and 205 perform the data transmission between the IC card and the reader/writer and receive electrical energy from the reader/writer.
The coils 204 and 205 are connected to a voltage rectification device 211 and a serial/parallel converter 214 in a switching element 210. The voltage rectification device 211 rectifies an alternating signal (AC signal) induced in the coils 204 and 205 and generates a direct voltage (DC voltage) U1. The DC voltage U1 is applied to an input terminal E1 of a comparator 212 and a power supply terminal E4 of the comparator 212 through a diode D1. The DC voltage U1 is also applied to a serial/parallel converter 214. The serial/parallel converter 214 is connected to a multiplexer 213.
Signal lines I1 through I6 are connected to the multiplexer 213. The signal line I6 (it is also referred to as a power supply line I6), which receives electrical energy from the contact terminal 203, is connected to an input terminal E2 and the power supply terminal E4 through a diode D2.
The comparator 212 compares a voltage at the input terminal E1 with a voltage at the input terminal E2 and outputs a select signal as a result of the comparison from an output terminal E3. The multiplexer 213 selects the serial/parallel converter 214 in response to the select signal when the voltage at the input terminal E1 is higher than the voltage at the input terminal E2 and selects the contact terminal 203 in response to the select signal when the voltage at the input terminal E1 is lower than the voltage at the input terminal E2. A microprocessor 220 is connected to the multiplexer 213.
When the IC card illustrated in FIG. 2 operates in the contact mode, the power supply voltage (electrical energy) is supplied from the contact terminal 203. The power supply voltage is transferred to the input terminal E2 and the power supply terminal E4 through the power supply line I6. At this time, since AC signal is not induced in the coils 204 and 205, DC signal U1 is not generated by the voltage rectification device 211. Thus, the comparator 212 outputs the select signal so that the multiplexer 213 selects the contact terminal 203. As a result, the microprocessor 220 is connected to the reader/writer through the contact terminal 203.
When the IC card illustrated in FIG. 2 operates in the contact-free mode, the voltage rectification device 211 rectifies AC signal induced in the coils 204 and 205 and generates the DC voltage U1. The DC voltage U1 is transferred to the input terminal El and the power supply terminal E4. At this time, since the power supply voltage is not supplied to the power supply line 16, the comparator 212 outputs the select signal so that the multiplexer 213 selects the serial/parallel converter 214. Thus, the microprocessor 220 is magnetically coupled to the reader/writer through the coils 204 and 205.
However, such this conventional IC card has a problem to be solved as explained bellow.
In a case where a strong alternating signal is induced in the coils 204 and 205 due to the noise etc. when the IC card operates in the contact mode (that is, the contact terminal 203 is contacted with the reader/writer), the voltage rectification device 211 rectifies the induced alternating signal and generates DC voltage U1. If the generated DC voltage U1 exceeds the power supply voltage supplied to the power supply line I6 through the contact terminal 203, the voltage at the input terminal E1 of the comparator 212 exceeds the voltage at the input terminal E2. At this time, the selection of the multiplexer 213 changes to the other selection. That is, although the IC card operates in the contact mode, the multiplexer 213 selects the serial/parallel converter 214 in response to the selection signal output from the output terminal E3. As a result, the microprocessor 220 may not continue to operate in the contact mode.
Consequently, there has been a need for an IC card that can keep an operation of the contact mode even though undesirable AC signal is induced in the coils due to the noise.
It is an object of the present invention is to provide an integrated circuit card that is seldom influenced by noise.
According to an aspect of the present invention, for achieving one or more of the above objects, there is provided a semiconductor integrated circuit that includes terminals for receiving data, a first control signal and a power supply by mechanical contact to the terminals and a coil for receiving data, a second control signal and a power supply by electromagnetic induction. The integrated circuit card also includes a mode designating circuit for designating a contact mode prior to the second control signal during the first control signal is received therein and for designating a contact-free mode during the second control signal is received therein. The integrated circuit card further includes a processing circuit for operating in the contact mode based on the contact mode designated by the mode designating circuit and for operating in the contact-free mode based on the contact-free mode designated by the mode designating circuit.
The above and further objects and novel features of the invention will more fully appear from the following detailed description, appended claims, and accompanying drawings.